Method of making miniature gas discharge tubes



Jan. 18, 1966 P. J. KAYATT METHOD OF MAKING MINIATURE GAS DISCHARGE TUBES i F Wm Filed Jan. 29, 1962 INVENTOR. PHfifP J KAY 2411 BY E. 5W

United States Patent 3,230,028 METHQD OF MAKING MINIATURE GAS DISCHARGE TUBES Philip J. Kayatt, 3636 Greystone Ave, New York, NX. Filed Jan. 29, 1962, Ser. No. 169,245 2 (llairns. (Cl. 316-20) The present invention relates to a miniature gas discharge tube and to a method for making the same.

The gas discharge tube consists of a pair of electrodes enclosed in a short envelope formed of small diameter glass tubing. At each end of the envelope a lead wire enters the tubing through a metal-to-glass seal. The spacing between the two lead wires exteriorly of the glass envelope consists of the full length of the tube. The lateral surface of the discharge tube is smooth and continuous being free from lateral seals or protrusions which would be inherent in a tube of this type produced by conventional methods.

The method involves the sealing of a first lead wire into one end of a length of glass tubing, the other end being left open. The second lead wire is then inserted and positioned in the open-ended portion of the tubing to provide the desired inter-electrode spacing. The open end of the tubing is connected to conventional evacuating and filling apparatus so that the air is removed and the tube filled with the desired gas at the desired pressure. When the evacuation and filling has been completed, a second and final metal-to-glass seal with the second lead wire is formed intermediate the ends of the tubing with the open end still connected to the evacuating and filling apparatus. The second metal-to-glass seal closes off a short length of the glass tubing which contains the two lead wires and the electrodes, if any, properly spaced, the electrodes being surrounded by the desired gas at the desired pressure. The openended portion of the glass tubing is then cut off and discarded. Any surplus length of the second lead wire is also cut off.

The invention will be better understood by reading the following specification, reference being had to the accompanying drawing forming a part hereof.

Referring to the drawing:

FIGURE 1 is a sectional view showing the glass tubing connected to the evacuating and filling apparatus.

FIGURE 2 is similar to FIG. 1 and shows the formation of the final metal-to glass in the tubing before removal from the evacuating and filling apparatus.

FIGURE 3 is a sectional view of the completed gas discharge tube.

FIGURE 4 is a sectional view gas discharge tube produced by vention.

Referring to FIG. 1, a length of glass tubing designated generally as 10 is closed at one end by a direct metal-toglass seal 11 through which a first lead wire 12 enters the interior of the tubing. Conveniently, the tubing 10 may have an external diameter of about 7 and an internal diameter of about 5 Smaller tubing may also be used. The lead wire 12 is formed of a metal having the same thermal coefiicient of expansion as the glass, the metal being conventional. Such a metal may be platinum or a suitable alloy well known in the art. The lead wire 12 is shown supporting an electrode 13 which may have any desired configuration. The electrode 13 may be omitted in certain instances. If this is done, the lower free end portion of the lead wire 12 within the tubing will serve as an electrode.

The electrode 13 cooperates with another electrode 14 mounted on the upper free end portion of a second lead wire 15. The lead wire 15 is shown bent at longitudinally spaced points 16 so that it fn'ctionally engages the interof a modified form of the method of the in- 3,230,028 Patented Jan. 18, 1966 nal surface of the glass tubing 10. This frictional engagement permits the inter-electrode spacing between the electrodes 13 and 14 to be accurately adjusted before the open end 17 of the tubing 10 is inserted in the resilient tubing 13 of the evacuating and filling apparatus 19. The force of frictional engagement between the bends at points 16 and the internal surface of the tubing 10 is suificient to prevent the electrode 14 from moving relative to the electrode 13 after the correct inter-electrode spacing has been set.

After evacuation to remove the air and subsequent filling with the desired gas at the desired pressure, and while the open end 17 remains connected to the evacuating and filling apparatus 19, the glass tubing 10 is heated in the region indicated by the reference numeral 20 so that the glass is softened and a direct metal-to-glass seal formed between the second lead wire 15 and the tubing 10. When the diameter of the tubing 10 permits, the tubing 10 may advantageously have a neck formed therein in the region 20 as indicated by dotted lines at 20a. The neck 20a is formed before insertion of the second lead wire 15 and facilitates the formation of the seal. This seal is the metal-to-glass seal 21 shown in FIGS. 2 and 3.

After the seal 21 has been formed, as shown in FIG. 2, the lower portion of the tubing 10 with the open end 17 is cut off below the seal 21 to produce the finished tube shown in FIG. 3. If desired, the lead wire 15 is cut to shorten it and it may also be straightened.

As shown in FIG. 3, the finished tube consists of a short length 22 (about /2") of the original tubing 10 with a metal-to-glass seal 11 at one end and a metal-to-glass seal 21 at the other end. The interior of the tubing 22 contains the desired gas at the desired pressure. The correct spacing between the electrodes 13 and 14 is retained as originally adjusted prior to evacuation, filling, and forming the final metal-to-glass seal 21. The walls of the tube 22 are smooth and continuous, being entirely free from any seals for purposes of conventional evacuation and filling. The lead wires 12 and 15 enter opposite ends of the tube thereby providing the maximum possible surface creepage distance for electrical insulation purposes.

FIG. 4 shows a modified form of tube wherein the free ends 24 and 25 of the lead wires 12 and 15, respectively, are parallel and laterally spaced within the tube 22. The tube of FIG. 4 is produced as described above.

While I have shown and described what I believe to be the best embodiments of my invention, it will be apparent to those skilled in the art that various modifications and changes may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. The method of forming a gaseous discharge tube which comprises the steps of: forming a first metal-toglass seal at one end of a length of glass tubing through which a first lead wire enters one end of said tubing, the other end being left open, inserting a second lead wire into said tubing through said open end, positioning a portion of said second lead wire intermediate its ends longitudinally of said tubing in frictional engagement therewith, evacuating and filling said tubing through said open end while retaining the positioning of said second lead wire, forming a second metal-to-glass seal between said tubing and said second lead wire while retaining said tubing in its evacuated and filled condition and retaining the positioning of said second lead wire, said second seal being formed intermediate said open end and said first seal, and severing the portion of said tubing including said open end which extends beyond said second seal.

2. The method according to claim 1, comprising the further step of bending said second lead Wire, prior to said inserting step, said Wire thereby being bent so that it frictionally engages the internal surface of said tubing after insertion therein, said step of retaining said posi- 5 tioning being effected by frictional engagement between said bent lead Wire and said internal surface.

References Cited by the Examiner Biggs 313182X Swanson 3 13-274 Dunn 313318X Chilcot et a1.

Wiener.

Cohen 25 0-106 Wiedenmann 313266 Belknap 313274 FOREIGN PATENTS Great Britain.

JOHN W. HUCKERT, Primary Examiner.

JAMES D. KALLAM, A. M. LESNIAK,

Assistant Examiners. 

1. THE METHOD OF FORMING A GASEOUS DISCHARGE TUBE WHICH COMPRISES THE STEPS OF: FORMING A FIRST METAL-TOGLASS SEAL AT ONE END OF A LENGTH OF GLASS TUBING THROUGH WHICH A FIRST LEAD WIRE ENTERS ONE END OF SAID TUBING, THE OTHER END BEING LEFT OPEN, INSERTING A SECOND LEAD WIRE INTO SAID TUBING THROUGH SAID OPEN END, POSITIONING A PORTION OF SAID SECOND LEAD WIRE INTERMEDIATE ITS ENDS LONGITUDINALLY OF SAID TUBING IN FRICTIONAL ENGAGEMENT THEREWITH, EVACUATING AND FILLING SAID TUBING THROUGH SAID OPEN END WHILE RETAINING THE POSITIONING OF SAID SECOND LEAD WIRE, FORMING A SECOND METAL-TO-GLASS SEAL BETWEEN SAID TUBING AND SAID SECOND LEAD WIRE WHILE RETAINING SAID TUBING IN ITS EVACUATED AND FILLED CONDITION AND RETAINING THE POSITIONING OF SAID SECOND LEAD WIRE, SAID SECOND SEAL BEING FORMED INTERMEDIATE SAID OPEN END AND SAID FIRST SEAL, AND SEVERING THE PORTION OF SAID TUBING INCLUDING SAID OPEN END WHICH EXTENDS BEYOND SAID SECOND SEAL. 